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Questions and Answers
What hormone is secreted by the supraoptic nucleus?
What hormone is secreted by the supraoptic nucleus?
Which structure connects the hypothalamus to the pituitary gland?
Which structure connects the hypothalamus to the pituitary gland?
Which part of the brain is primarily responsible for the coordination of somatic motor function?
Which part of the brain is primarily responsible for the coordination of somatic motor function?
Which nucleus regulates circadian rhythm?
Which nucleus regulates circadian rhythm?
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Which lobe of the brain is responsible for perceiving auditory stimuli?
Which lobe of the brain is responsible for perceiving auditory stimuli?
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What role does the pre-optic area play in brain function?
What role does the pre-optic area play in brain function?
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Which part of the brain is involved in the subconscious coordination of movement?
Which part of the brain is involved in the subconscious coordination of movement?
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Which structure separates the left and right hemispheres of the cerebrum?
Which structure separates the left and right hemispheres of the cerebrum?
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What is the primary function of the Gi pathway?
What is the primary function of the Gi pathway?
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Which process is initiated by the Gq pathway upon ligand binding?
Which process is initiated by the Gq pathway upon ligand binding?
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What role does IP3 play in the Gq signaling pathway?
What role does IP3 play in the Gq signaling pathway?
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Which characteristic is NOT associated with epithelial tissue?
Which characteristic is NOT associated with epithelial tissue?
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The basal lamina has which of the following components?
The basal lamina has which of the following components?
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What is a key feature of simple epithelium?
What is a key feature of simple epithelium?
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What is the primary role of protein kinase A?
What is the primary role of protein kinase A?
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What does the reticular lamina consist of?
What does the reticular lamina consist of?
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Which artery is primarily responsible for supplying blood to the cerebellum?
Which artery is primarily responsible for supplying blood to the cerebellum?
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What is the typical range of intracranial pressure (ICP)?
What is the typical range of intracranial pressure (ICP)?
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How is cerebral perfusion pressure calculated?
How is cerebral perfusion pressure calculated?
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What is the primary function of the Circle of Willis?
What is the primary function of the Circle of Willis?
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Which neurotransmitter is primarily involved in the synaptic transmission at the neuromuscular junction?
Which neurotransmitter is primarily involved in the synaptic transmission at the neuromuscular junction?
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What happens if mean arterial pressure (MAP) falls below 65 mmHg?
What happens if mean arterial pressure (MAP) falls below 65 mmHg?
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Which structure is primarily involved in producing and breaking down acetylcholine?
Which structure is primarily involved in producing and breaking down acetylcholine?
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Which of the following arteries branches from the external carotid artery?
Which of the following arteries branches from the external carotid artery?
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What is the primary role of acetylcholinesterase in neurotransmission?
What is the primary role of acetylcholinesterase in neurotransmission?
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Which condition is primarily associated with autoimmune destruction of nicotinic receptors?
Which condition is primarily associated with autoimmune destruction of nicotinic receptors?
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What neurotransmitter is primarily implicated in the reward pathways and addiction?
What neurotransmitter is primarily implicated in the reward pathways and addiction?
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How does serotonin primarily terminate its actions within the synapse?
How does serotonin primarily terminate its actions within the synapse?
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What is the main function of NMDA receptors in neurotransmission?
What is the main function of NMDA receptors in neurotransmission?
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What occurs as a result of excessive activity of dopamine in the brain?
What occurs as a result of excessive activity of dopamine in the brain?
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Which of the following statements about glutamate is true?
Which of the following statements about glutamate is true?
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What impact does the enzyme monoamine oxidase (MAO) have on biogenic amines?
What impact does the enzyme monoamine oxidase (MAO) have on biogenic amines?
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What is the primary role of the vagus nerve concerning heart rate?
What is the primary role of the vagus nerve concerning heart rate?
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Which layer of a blood vessel contains smooth muscle?
Which layer of a blood vessel contains smooth muscle?
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What characteristic distinguishes arteries from veins?
What characteristic distinguishes arteries from veins?
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Which type of artery is most resistant and utilizes recoil during diastole to aid blood flow?
Which type of artery is most resistant and utilizes recoil during diastole to aid blood flow?
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What is the diameter of arterioles?
What is the diameter of arterioles?
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Which type of capillary has pores to increase the exchange rate?
Which type of capillary has pores to increase the exchange rate?
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Which part of the aorta receives freshly oxygenated blood?
Which part of the aorta receives freshly oxygenated blood?
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What characterizes the systemic circuit in terms of blood pressure and vessel walls?
What characterizes the systemic circuit in terms of blood pressure and vessel walls?
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Study Notes
G-Protein Pathways
- Gi inhibits cAMP production, which is similar to the Gs pathway but instead inhibits the conversion of ATP to cAMP
- Protein Kinase A phosphorylates proteins, which can cause changes in enzyme activity, transporter activity, and ion channel activity
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Gq uses IP3 and DAG as second messengers to activate protein kinases.
- Ligand binding activates the alpha subunit of the G-protein
- The alpha subunit then activates PLC (phospholipase C)
- PLC converts PIP2 into IP3 and DAG
- DAG activates PKC (protein kinase C), which in turn phosphorylates proteins and elicits cellular responses
- IP3 binds to calcium channels on the ER and causes calcium efflux
- Calcium complexes with calmodulin, triggering additional responses and/or activating protein kinases for phosphorylation
cGMP
- Cyclic guanosine monophosphate, produced from GTP by guanylate cyclase
- Activates protein kinase G and acts on other effectors
Epithelial Tissue
- Covers exposed surfaces, lining internal passageways for protection, sensation, and permeability control
- Produces glandular secretions individually or as a unit
- Cellularity: Epithelial cells tend to be bound tightly
- Polarity: The apical surface is exposed, while the basal surface remains attached to tissue; each surface is specialized for a specific function
- Attachment: The basal surface attaches to a basement membrane
- Avascularity: Epithelial tissue lacks blood vessels and must absorb nutrients from surrounding surfaces
- Sheets: Epithelial tissue forms thin sheets of cells, one or more layers thick
- Regeneration: Stem cells replace lost or damaged epithelial cells
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Basement Membrane: Attaches to the basal surface of most epithelial cells
- Basal Lamina: Secreted by epithelial cells, directly attaches to the basal surface, consists of glycoproteins, proteoglycans, and microfilaments, restricts the movement of large molecules from connective tissue into the epithelium
- Reticular Lamina: Secreted by connective tissue, consists of coarse protein fibres that anchor the basement membrane to the connective tissue
- Simple Epithelium: A single layer of cells, found in unexposed areas, with uniform polarity and shape, facilitates diffusion, attached to a basement membrane and can regenerate
Hypothalamus
- Involved in emotions, thirst, and some habitual activity
- Extends from above the optic chiasm to mammillary bodies
- Subconsciously controls skeletal muscle and other visceral functions (e.g. heart rate)
- Infundibulum: Connects the pituitary gland to the hypothalamus
- Tuberal Area: Midsagittal section of the hypothalamus
- Supraoptic Nucleus: Secretes ADH
- Paraventricular Nucleus: Secretes oxytocin
- Pre-Optic Area: Regulates body temperature
- Suprachiasmatic Nucleus: Regulates circadian rhythm
- Autonomic Centres: Controls heart rate and BP via regulation of the medulla oblongata
Cerebellum
- Second largest brain part with 2 hemispheres
- Coordinates somatic motor function and adjusts output of somatic motor centres for smooth function
- Folia Cerebri: Folds similar to gyri of the cerebellum
- Primary Fissure: Separates anterior and posterior lobes
- Vermis: Narrow band of cortex that separates the hemispheres
- Cerebellar Cortex: Controls subconscious coordination of movement
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Arbor Vitae: Connects cerebellar cortex with cerebellar peduncles
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Cerebellar Peduncles: Divided into three types based on location:
- Superior: Connects cerebellum with midbrain, diencephalon and cerebrum
- Middle: Communicates between cerebellum and pons
- Inferior: Connects cerebellum and medulla oblongata
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Cerebellar Peduncles: Divided into three types based on location:
Cerebrum
- Largest portion of the brain with a surface consisting of gray matter
- Responsible for consciousness, intellectual functions, memory storage, and conscious function of skeletal muscle
- Has 2 hemispheres separated by a longitudinal fissure
- Sulci: "Grooves" in the cerebrum
- Gyri: "Ridges" in the cerebrum
- Longitudinal Fissure: Separates hemispheres
- Corpus Callosum: Connects left and right hemispheres
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Lateral Sulcus/Fissure: Separates temporal, frontal, and parietal lobes
- Insula: Located deep within the lateral sulcus, responsible for sensory, motor, emotion, and cognitive functions
- Central Sulcus: Separates frontal and parietal lobes
- Frontal Lobe: Consciously controls skeletal muscles
- Temporal Lobe: Consciously perceives auditory/olfactory stimuli, as deep as the insula
- Parietal Lobe: Consciously perceives touch, pressure, vibration, pain, temperature, and taste
- Occipital Lobe: Responsible for vision
- Precentral Gyrus: Anterior to the central gyrus, contains pyramidal cells that direct voluntary movements through control of motor neurons, part of the primary motor cortex
- Postcentral Gyrus: Posterior to the central sulcus, covers frontal, parietal, and temporal lobes
Arterial System
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External Carotids: Supply the neck and outside of the skull, branches into:
- Lingual artery
- Facial artery
- Occipital artery
- Superficial temporal artery
- Vertebral Arteries: Has a left and right, originate from vertebrae
- Basilar Artery: Fusion of both vertebral arteries, supplies pons, medulla, and midbrain
- Posterior Cerebral Artery + Posterior Communicating Artery: Connect basilar artery and internal carotid arteries, supplies inferior and medial temporal/occipital lobes, including the hippocampus, thalamus, and primary visual cortex
- Circle of Willis (Cerebral Arterial Circle): Ring-like anastomosis between the basilar and carotid arteries, functions as a safety mechanism for blood supply from carotids and vertebral arteries
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Cerebellar Arteries: Arteries that supply the cerebellum:
- Superior cerebellar
- Anterior inferior cerebellar
- Posterior inferior cerebellar
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Cerebral Perfusion Pressure (CPP): Pressure at which blood is delivered to the brain at the capillary level, calculated by subtracting ICP from MAP
- ICP (Intracranial Pressure): Typically 5-15mmHg; anything over 20 can cause perfusion issues and the loss of cerebral blood flow
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MAP (Mean Aortic Pressure): Mean aortic pressure over the cardiac cycle, 60-150mmHg, should be kept above 65mmHg for optimal systemic perfusion, regulated by negative feedback through baroreceptors and the ANS
- If too low: Hypotension and inadequate perfusion
- If too high: Hypertension, stressed heart and vessels
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Aorta: Largest vessel in the body, splits into three components:
- Ascending Aorta: First part of the aorta that receives freshly oxygenated blood, splits off into coronary arteries at its base
- Aortic Arch: Top portion of the aorta, branches into several vessels, some of which subdivide further
Neurotransmitters
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Acetylcholine: Produced by converting Acetyl CoA and choline using choline acetyl transferase (CAT)
- Acetylcholinesterase: Breaks down acetylcholine in the synaptic cleft, producing acetate and choline
- Nicotinic Receptors: Ionotropic, involved with reward and anti-anxiety pathways, acetylcholine is the main ligand
- Muscarinic Receptors: Metabotropic, located at the NMJ and inside the ANS, acetylcholine is the main ligand
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Synaptic Transmission:
- Acetylcholine is made using CAT
- Vesicles store acetylcholine
- An arriving action potential opens voltage-gated calcium channels
- Vesicle docking is triggered and acetylcholine is secreted
- Acetylcholine binds to a postsynaptic receptor, causing a response in the postsynaptic cell
- Acetylcholinesterase breaks down free acetylcholine into choline and acetate
- Byproducts are recycled back into the axon terminal
- Alzheimer’s Disease: Progressive degeneration of cholinergic neurons at the base of the forebrain, caused by amyloid plaques and neurofibrillary tangles, causes a loss of cholinergic input from the basal forebrain, symptoms include memory loss, language, motor, and perception deficits alongside chronic confusion
- Myasthenia Gravis: Most commonly caused by autoimmune destruction of nicotinic receptors of the motor endplate, causes weakness of muscles and drooping of eyes, treated using acetylcholinesterase inhibitors
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Biogenic Amines: Includes catecholamines, serotonin, and histamine
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Catecholamines: Type of neurotransmitter derived from tyrosine, includes epinephrine, norepinephrine, and dopamine
- Dopamine: Binds to dopaminergic neurons, synthesized from L-DOPA, loss of activity can cause motor deficits (Parkinson’s), excess activity is implicated in schizophrenia, key component of reward pathways, heightened activity associated with substance addiction
- Noradrenaline: Synthesized by dopamine beta hydroxylase from dopamine, deficits of adrenergic activity associated with depression
- Monoamine Oxidase (MAO): Breaks down biogenic amines
- COMT: Inactivates biogenic amines through methylation
- Serotonin/5-HT: Derived from tryptophan, binds to 5-HT receptors, actions terminated by SERT (blocked by SSRI for depression treatment) in addition to MAO, cell bodies mainly located in the brainstem with widespread projections, main roles include sensory/motor function, mood, anxiety, and regulation of pain
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Catecholamines: Type of neurotransmitter derived from tyrosine, includes epinephrine, norepinephrine, and dopamine
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Glutamate: Amino acid transmitter, main excitatory CNS neurotransmitter, can bind to some metabotropic receptors that mostly mediate inhibitory responses but also binds to ionotropic receptors, plays roles in long-term potentiation and several mental disorders
- AMPA Receptors: Ionotropic, sodium channel
- Kainate Receptors: Ionotropic, sodium channel, overactivation can result in excitotoxicity
- NMDA Receptors: Ionotropic, calcium channel regulated by magnesium, inhibited by phencyclidine and memantine, glutamate acts as a co-agonist with glycine
- Aspartate: Works in a similar fashion as glutamate, activates parasympathetic neurons and decreases heart rate, innervated by the vagus nerve
Blood Vessels
- Outer Adventitia: Outermost layer of a blood vessel that anchors it
- Media: Middle layer of a blood vessel that is lined with smooth muscle, can constrict or dilate a vessel
- Intima: Endothelium of a vessel
- Arteries: Carry blood away from the heart, thicker walls, more smooth muscle, thin elastic membranes in media and intima, no valves, retain their circular shape when cut, endothelial lining has pleated folds
- Veins: Carry blood towards the heart, thinner walls, less smooth muscle, no pleated folds and no elastic membranes compared to arteries, collapse when cut, contain one-way valves to prevent blood backflow
- Elastic Arteries: 2.5cm diameter arteries with all elastic membranes, very resistant and uses recoil during diastole to pump blood forward, aorta, pulmonary trunk, brachiocephalic trunk
- Muscular Arteries: 0.4cm in diameter, can be changed by ANS control, radial, ulnar, external carotid, brachial, femoral, mesenteric arteries
- Arterioles: 30 micron diameter arteries with thin adventitia, has incomplete muscle layers in media but can still control blood flow between arteries and capillaries
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Capillaries: 8 micron diameter, incredibly delicate without any adventitia or media, responsible for material exchange
- Continuous: Capillaries with complete endothelial lining, most common type found in the CNS/skin
- Fenestrated: Capillaries with incomplete endothelial lining using pores to increase exchange rate, found in the kidneys, small intestine, and endocrine glands
- Sinusoids/Discontinuous: Capillaries that have incomplete endothelial lining with large gaps and pores, found in the liver, spleen, and lymph nodes
- Systemic Circuit: Describes blood flow all over the body, has a lower blood pressure than the pulmonary circuit, with thicker walls to facilitate long-distance travel
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Description
Explore the intricate mechanisms of G-Protein pathways, including the roles of Gi, Gq, and cGMP in cellular signaling. Understand how these pathways influence protein phosphorylation and cellular responses through various second messengers. Test your knowledge on the key components and functions of these vital signaling pathways.
